Yoshiaki Ozaki

High Resolution Neutron Spectrometer LAM-80ETand Rotational Tunnelling in 4-Methylpyridine N-Oxide

A high energy-resolution neutron spectrometer with large mica mirrors, LAM-80ET, has been constructed at National Laboratory for High Energy Physics in Japan (KEK). The highest resolution achieved with this spectrometer is 1.2 µeV. In order to examine the capability of the spectrometer, the rotational tunnelling of the methyl group in 4-methyl pyridine N-oxide (N-oxy γ-picoline) has been measured. Using the (004) reflection of the mica mirrors, we have clearly observed four peaks at e=60, 115, 190 and 274 µeV. Measurements of the Q -dependence of these tunnelling peaks show that the tunnelling potential may be three-fold. It is also shown that the line width of tunnelling modes and the spin conversion at T >5 K are derived by the libron-phonon process with E L =30-40 K.

Rotational States of NH+4 in Dilute Solution in Alkali Halide Lattices. V. Calculated Intensities of Neutron Scattering of NH+4 in KBr

The intensity of neutron scattering for tunnel splitting levels of NH + 4 ion is calculated in terms of the orientationally localized states. The k -dependence of the transition integral and the temperature dependence of the spectra are derived. In conclusion, C 3 v , orientation is the best model to yield the observed spectra and two big additional peaks are anticipated in E >3 meV.

Rotational States of NH+4 in Dilute Solution in Alkali Halide Lattices. III. Calculated Energy Levels of NH+4 in KBr

The rotational energy levels of NH + 4 in dilute solution in KBr have been calculated for three possible orientations of a tetrahedral ion in an octahedral field. Both tunneling and librational levels have been obtained. It is concluded that the inelastic neutron scattering spectra, which were reported in part I [J. Phys. Soc. Jpn. 52 (1983) 2401], are best accounted for on the basis of C 3v orientation of the NH + 4 ions on the cation lattice sites.

Calculation of Rotational Energy Levels of CH4 in Solid Ar

M. Prager et al . have shown by inelastic neutron scattering that the methane molecules dispersed in solid argon have two sites. It is inferred that the tetrahedral molecule receives not only the octahedral field at one site but the tetrahedral field at the other site. The latter field may be contributed from hcp structure in host atoms. The crystal field analysis is made in 3rd, 4th, and 6th orders using the conventional atom-atom potentials. It is concluded that C 3v configuration is dominant in fcc lattice while T d one in hcp lattice. In addition, rotational energy levels are computed in terms of the estimated field parameters. The result is compatible with the observed neutron scattering spectra.

CALCULATION OF ROTATIONAL STATES OF METHANE MOLECULES IN A SQUARE LATTICE

Abstract Methane molecules in a square lattice perform hindered rotation due to the molecular interaction. First, the one-body term in the interaction gives the new pattern of rotational energy level scheme. In the case of strong interaction, this scheme becomes similar to tunneling levels calculated from the pocket state formalism. Secondly, the two-body term produces a potential with lower symmetry. We investigate the case of a ferro-orientational phase. Four levels remain in the lowest part of rotational energy spectrum under the field strength estimated from the sum of atom–atom pair potentials. This small number of levels approaches to more realistic systems.

Ab Initio Interatomic Potential Curves for NaNO2 and the Simulation of the Molten Salt

Ab initio potential energy curves are presented for (Na + )(NO - 2 ) as a function of the Na–N separation. The minimum energy configuration , is similar to that observed in the room temperature ferroelectric solid. Empirical atom-atom potential energy functions based in part on the ab initio calculations, are used in a molecular dynamics computer simulation of the molten salt.

Rotational states of the ammonium ion in cubic lattice

The ammonium ion in the alkali halide lattice has the hindered rotational state. The rotational potential is expressed as crystal field, which depends upon only one rotational motion. The tetrahedral ion receives an octahedral field in this system. Four fundamental types of orientation appear due to the symmetry of ion and that of field. As the barrier height increases, the rotational levels approach to the librational levels with tunnel splitting. In particular, the tunneling part in the ground librational level is calculated using both free rotor bases and orientationally localized states. The level structure with the degeneracy is elucidated, which is peculiar in each type of orientation. Thermal properties are shown as model calculations.

Calculation of rotational tunneling states of the methyl group in the higher order of potential

The intensities are calculated of inelastic neutron scattering for the protons of methyl group in hindering potential. Orientationally localized states are employed as rotational bases. The Q‐dependence of intensity of each peak is derived in the case of 3‐fold and 6‐fold potentials.

Octahedral molecules in a cubic field

Abstract In a solid or rare-gas matrix, a spherical molecule can rotate fairly freely in some cases. There is a variation in both strength and symmetry of the hindrance potential, according to the type of molecular and lattice symmetry. The tetrahedral molecule has been investigated so far in detail by many kinds of experiment, including neutron scattering. However, an octahedral molecule like AX 6 has been studied in detail neither by experiment nor theoretically. In order to clarify the difference in the symmetry, we evaluate the rotational potential in the case of SF 6 , molecule in a tetrahedral cage.